Add sourceFactory getter to AnalysisSession

pkg/analyzer/lib/src/dart/analysis/session.dart

 // Copyright (c) 2017, the Dart project authors. Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 import 'dart:async';
 
 import 'package:analyzer/dart/analysis/results.dart';
 import 'package:analyzer/dart/analysis/session.dart';
 import 'package:analyzer/dart/element/element.dart';
 import 'package:analyzer/src/dart/analysis/driver.dart' as driver;
@@ skipping 19 matching lines @@
    * The type system being used by the analysis driver.
    */
   TypeSystem _typeSystem;
 
   /**
    * Initialize a newly created analysis session.
    */
   AnalysisSessionImpl(this._driver);
 
   @override
+  SourceFactory get sourceFactory => _driver.sourceFactory;
+
+  @override
   Future<TypeProvider> get typeProvider async {
     _checkConsistency();
     if (_typeProvider == null) {
       LibraryElement coreLibrary = await _driver.getLibraryByUri('dart:core');
       LibraryElement asyncLibrary = await _driver.getLibraryByUri('dart:async');
       _typeProvider = new TypeProviderImpl(coreLibrary, asyncLibrary);
     }
     return _typeProvider;
   }
 
@@ skipping 62 matching lines @@
   /**
    * Check to see that results from this session will be consistent, and throw
    * an [InconsistentAnalysisException] if they might not be.
    */
   void _checkConsistency() {
     if (_driver.currentSession != this) {
       throw new InconsistentAnalysisException();
     }
   }
 }